Process for producing variable syngas compositions

Abstract

Disclosed is a process for the production of a variable syngas composition by gasification. Two or more raw syngas streams are produced in a gasification zone having at least 2 gasifiers and a portion the raw syngas is passed to a common water gas shift reaction zone to produce at least one shifted syngas stream having an enriched hydrogen content and at least one unshifted syngas stream. The shifted and the unshifted syngas streams are mixed downstream of the water gas shift zone in varying proportions produce blended and unblended synthesis gas streams in a volume and/or composition that may vary over time in response to at least one downstream syngas requirement. The process is useful for supplying syngas from multiple gasifiers for the variable coproduction of electrical power and chemicals across periods of peak and off-peak power demand.

1 . A process for producing variable syngas compositions, comprising: 
 (a) reacting an oxidant stream with a carbonaceous material in a gasification zone comprising at least 2 gasifiers to produce at least 2 raw syngas streams comprising carbon monoxide, hydrogen, carbon dioxide, and sulfur-containing compounds,    (b) passing a portion of at least one of said raw syngas streams from step (a) to a common water-gas shift reaction zone to produce at least one shifted syngas stream (i) having an enriched hydrogen content, and at least one unshifted syngas stream (ii), comprising a remaining portion of said raw syngas streams; and    (c) blending said shifted syngas stream (i) with a portion of said unshifted syngas stream (ii) to produce at least one blended syngas stream (iii) and at least one unblended syngas stream (iv) comprising a remaining portion of unshifted syngas stream (ii) wherein said blended syngas stream is produced in a volume and/or composition that varies in response to at least one downstream syngas requirement.    
     
     
         2 . The process according to  claim 1  further comprising generating steam in said water-gas shift reaction zone.  
     
     
         3 . The process according to  claim 2  further comprising combining a portion of said steam from said water-gas shift reaction zone with said portion in step (b) of one or more raw syngas streams to produce at least one wet syngas stream and passing said wet syngas stream to said water-gas shift reaction zone.  
     
     
         4 . The process according to  claim 3  wherein the molar ratio of water to carbon monoxide in said wet syngas stream is about 1.5:1 to about 3:1.  
     
     
         5 . The process according to  claim 2  wherein said steam is generated by recovery of heat from said shifted syngas stream (i) before step (c).  
     
     
         6 . The process according to  claim 1  wherein said oxidant stream comprises at least 85 volume % oxygen, based on the total volume of said oxidant stream.  
     
     
         7 . The process according to  claim 6  wherein said oxidant stream comprises at least 95 volume % oxygen.  
     
     
         8 . The process according to  claim 1  wherein the carbonaceous material is coal or petroleum coke.  
     
     
         9 . The process according to  claim 1  further comprising passing each of said syngas streams (i) and (ii) from step (b) or each of said syngas streams (iii) and (iv) from step (c) through separate gas cooling zones.  
     
     
         10 . The process according to  claim 1  further comprising passing each of said syngas streams (i) and (ii) from step (b) or each of said syngas streams (iii) and (iv) from step (c) through separate acid gas removal zones.  
     
     
         11 . The process according to  claim 10  wherein said acid gas removal zones comprise a sulfur removal zone in which at least 95 mole percent of the total of said sulfur containing compounds present in said syngas streams (i) and (ii) or (iii) and (iv) are removed.  
     
     
         12 . The process according to  claim 11  wherein said downstream syngas requirement comprises a feedstock need of a least one chemical process, a fuel need of at least one power plant, or a combination thereof.  
     
     
         13 . The process according to  claim 1  further comprising (d) passing said blended syngas stream (iii) to a chemical producing zone and said unblended syngas stream (iv) to a power producing zone.  
     
     
         14 . The process according to  claim 13  wherein said chemical producing zone produces methanol, alkyl formates, dimethyl ether, oxo aldehydes, ammonia, methane, hydrogen, Fischer-Tropsch products, or a combination thereof.  
     
     
         15 . The process according to  claim 14  wherein said chemical producing zone is a methanol producing zone.  
     
     
         16 . The process according to  claim 15  further comprising removing a portion of said carbon dioxide from said syngas streams (i) or (iii) to give a carbon dioxide concentration of about 0.5 to about 10 mole %, based on the total moles of gas in said syngas streams (i) or (iii), before passing to said methanol-producing zone of step (d).  
     
     
         17 . The process according to  claim 13  wherein said power producing zone comprises a combined cycle system.  
     
     
         18 . The process according to  claim 13  wherein said volume and/or composition of said blended syngas stream varies in response to peak and off-peak power demands.  
     
     
         19 . A process for producing variable syngas compositions, comprising: 
 (a) reacting an oxidant stream with coal or petroleum coke in a gasification zone comprising at least 2 gasifiers to produce at least 2 raw syngas streams comprising carbon monoxide, hydrogen, carbon dioxide, and sulfur-containing compounds,    (b) passing a portion of at least one of said raw syngas streams from step (a) to a common water-gas shift reaction zone to produce at least one shifted syngas stream (i) having a molar ratio of hydrogen to carbon monoxide of about 1:1 to about 20:1, and at least one unshifted syngas stream (ii), comprising a remaining portion of said raw syngas streams;    (c) generating steam in said water-gas shift reaction zone by recovery of heat from said shifted syngas stream (i);    (d) combining a portion of said steam from step (c) with said portion of one or more raw syngas streams before passing to said water-gas shift reaction zone;    (e) blending said shifted syngas stream (i) with a portion of said unshifted syngas stream (ii) to produce at least one blended syngas stream (iii) and at least one unblended syngas stream (iv) comprising a remaining portion of unshifted syngas stream (ii); and    (f) passing said blended syngas stream (iii) to a methanol or dimethyl ether producing zone and unblended syngas stream (iv) to a power producing zone.    
     
     
         20 . The process according to  claim 19  further comprising passing each of said syngas streams (i) and (ii) from step (b) or each of said syngas streams (iii) and (iv) from step (e) through separate gas cooling zones.  
     
     
         21 . The process according to  claim 19  further comprising passing each of said syngas streams (i) and (ii) from step (b) or each of said syngas streams (iii) and (iv) from step (e) through separate acid gas removal zones, comprising a sulfur removal zone, a carbon dioxide removal zone, or a combination thereof.  
     
     
         22 . The process according to  claim 21  further comprising removing at least 95 mole percent of the total sulfur-containing compounds present in said syngas streams (i) and (ii) or (iii) and (iv) in a sulfur removal zone.  
     
     
         23 . The process according to  claim 21  further comprising removing a portion of said carbon dioxide from syngas stream (iii) in a carbon dioxide removal zone.  
     
     
         24 . The process according to  claim 19  wherein said blended syngas stream (iii) is produced in a volume and/or composition that varies in response to peak and off-peak power demands.  
     
     
         25 . A process for producing variable amounts of power and methanol, comprising: 
 (a) reacting an oxidant stream with coal or petroleum coke in a gasification zone comprising at least 2 gasifiers to produce at least 2 raw syngas streams comprising carbon monoxide, hydrogen, carbon dioxide, and sulfur-containing compounds,    (b) passing a portion of at least one of said raw syngas streams from step (a) to a common water-gas shift reaction zone to produce at least one shifted syngas stream (i) having an enriched hydrogen content, and at least one unshifted syngas stream (ii), comprising a remaining portion of said raw syngas streams;    (c) blending said shifted syngas stream (i) with up to 100 volume percent of said unshifted syngas stream (ii) to produce at least one blended syngas stream (iii) and a remaining portion of said unshifted syngas stream (ii);    (d) producing methanol by passing said blended gas stream (iii) from step (c) to a methanol producing zone; and    (e) passing the remaining portion of unshifted syngas stream (ii) to a power producing zone to produce electrical power;    wherein said blended syngas stream is produced in a volume and/or composition that varies in response to periods of peak and off-peak power demands on said power producing zone.    
     
     
         26 . The process according to  claim 25  further comprising generating steam in said water-gas shift reaction zone by recovery of heat from said shifted syngas stream (i) before step (c).  
     
     
         27 . The process according to  claim 26  further comprising combining a portion of said steam from said water-gas shift reaction zone with said portion in step (b) of one or more raw syngas streams to produce at least one wet syngas stream and passing said wet syngas stream to said water-gas shift reaction zone.  
     
     
         28 . The process according to  claim 25  wherein said methanol producing zone comprises a fixed bed methanol reactor.  
     
     
         29 . The process according to  claim 25  wherein said methanol producing zone comprises a liquid slurry phase methanol reactor.  
     
     
         30 . The process according to  claim 25  wherein said 2 or more gasifiers are sized to supply at least 90% of the maximum capacity fuel requirements of said power-producing zone.  
     
     
         31 . The process according to  claim 25  further comprising passing each of said syngas streams present in steps (a), (b), or (c) through separate gas cooling zones.  
     
     
         32 . The process according to  claim 25  further comprising passing each of said syngas streams present in steps (a), (b), or (c) through separate acid gas removal zones.  
     
     
         33 . The process according to  claim 32  wherein said acid gas removal zones comprise a sulfur removal zone in which at least 95 mole percent of said sulfur containing compounds present in said syngas streams are removed.  
     
     
         34 . The process according to  claim 25  further comprising removing a portion of said carbon dioxide from said syngas streams (i) or (iii) to give a carbon dioxide concentration of about 0.5 to about 10 mole %, based on the total moles of gas in said syngas streams (i) or (iii), before passing to said methanol-producing zone of step (d).  
     
     
         35 . The process according to  claim 25  wherein 100 volume percent of said unshifted syngas stream (ii) is blended with said shifted syngas stream (i) during a period of off-peak power demand.